perldoc perlreftut and peldoc perlref can get you started with references. perldsc and perllol can walk you through manipulating datastructures built using references. I used map (perldoc -f map) to perform the actual data structure transform. But if you're new to some of this it might be easier to achieve the same thing using a foreach loop (perldoc perlsyn) and push (perldoc -f push):